rayward
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 posted on 20/1/03 at 07:45 PM |
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castor angle
have just tacked my front wishbone brackets on and have ended up with a castor angle of 5.05 degrees, i know the book says 5.30 +- .30, but how does
this affect hadling ???
thanks for any help
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stephen_gusterson
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| posted on 20/1/03 at 10:38 PM |
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i havnt driven my car on the road yet to confirm, but most people say that the book castor is a bit on the low side anyway.
Castor gives the steering a self centering effect.
There will be more techy types that can answer this question more fully 
atb
Steve
[Edited on 20/1/03 by stephen_gusterson]
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jollygreengiant
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| posted on 21/1/03 at 07:37 AM |
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quote:
Originally posted by rayward
have just tacked my front wishbone brackets on and have ended up with a castor angle of 5.05 degrees, i know the book says 5.30 +- .30, but how does
this affect hadling ???
thanks for any help
5.3 - 0.3 = 5.0, your =5.05 = within tolerance.
Providing you have the same angle each side then you WILL have a good self centring action, all that you will need is to get the tracking sorted
properly with 4 wheel alignment guages. Just try & find someone in your area who actually knows what he is doing.
Enjoy.
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Mark Allanson
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| posted on 21/1/03 at 07:40 PM |
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I have made my brackets wider so washers are needed to pack out the difference. I will be able to swap washers from the front to the rear of the
brackets to adjust the castor.
How have you measured the castor, the suspension will not have settled down until the car has covered about 500 miles (if production car rules of
thumb apply).
I have a Hunter computerised system at work that will measure to the accuracy you have measured, but it cost £18,000! You can measure a car one day,
drive it for 10 miles and remeasure and you still get small variations - it even seems to be affected by humidity and temperature.
I think you best bet would be to complete your build, run it for a few weeks and the book it in an approved bodyshop with the right facilities and
have it measured. It should cost about 1.5 hours at £23.50 per hour at current rates, more if you ask them to adjust anything. With 4 tyres costing
over £200 it could be a good investment, not to mention helping keeping your car shiney side up and pointing in the right direction!
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Mark Allanson
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| posted on 21/1/03 at 09:06 PM |
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I got curious about what adjustment I will get from my washer idea. The washers are 1mm stainless and (after scratching of head and asking kids about
basic trig) I have worked out that each washer will be worth a knats pubic hair over 0.3 degrees of castor. This asssumes that RC has got his sums
right that 18mm setback of the upper wishbone will give 5.5 degrees of castor.
It shows how accurate you need to be when setting your brackets and making your wishbones. The Hunter will confirm if I am an accurate engineer or a
crosseyed butcher!
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Rorty
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| posted on 22/1/03 at 03:52 AM |
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JollyGG:
quote:
5.3 - 0.3 = 5.0, your =5.05 = within tolerance. Providing you have the same angle each side then you WILL have a good self centring action, all that
you will need is to get the tracking sorted properly with 4 wheel alignment guages. Just try & find someone in your area who actually knows what he is
doing.
Good advice. You will, however, only have good centring action if the position of the front and rear wheels are a mirror image of the other side. If
you don't have a square footprint, then having equal castor isn't much use.
As JollyGG says, make sure the alignment specialist is exactly that. Get them to check the footprint before proceeding with anything else.
Of course, you can very easily check the footprint at home yourself. (which may actually avoid a potentially embarrasing situation!)
[Edited on 22/1/03 by Rorty]
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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PaulBuz
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| posted on 20/3/03 at 06:20 PM |
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Rorty, sorry to drag up an old post , but just how do I check to see if i have a square footprint?
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Peteff
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| posted on 20/3/03 at 06:31 PM |
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Square footprint.
I fastened some angle iron pieces to my wheel studs and checked they were upright with a spirit level, then I measured them diagonally. I got close to
the same measurements but I got fed up eventually and left it close. It seems to drive alright.
yours, Pete.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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stephen_gusterson
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| posted on 20/3/03 at 07:31 PM |
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that sounds like a good plan!
Have had wheels on mine for about a year and was dreading figuring out how to set up - approx - the final alignment.
Will give that idea a go!
atb
steve
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Rorty
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| posted on 21/3/03 at 02:46 AM |
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PaulBuz:
quote:
Rorty, sorry to drag up an old post , but just how do I check to see if i have a square footprint?
It's dead simple. You'll need a cleanly swept, level floor. Pick a prominent point somewhere near the front of the chassis, say the centre
of the hole in the front lower wishbone bracket. Drop a plumb line from your chosen point, and mark an X on the floor with a pencil or fine pen.
(we're talking to the nearest 0.5mm here!) Draw a circle around the X with a bit of chalk, so you don't lose sight of it.
Go to the other side of the car, and repeat the process. Do the same for the rear end.
When you have marked all four Xs on the floor, it's then a simple case of measuring diagonally across the rectangle. Any difference greater than
about 5mm will need to be rectified before you proceed.
You should also drop the plumb line from the front centre and rear centre, and put marks on the floor. Use a chalk line, and snap a line from one
centre mark to the other.
Once the chassis has been checked for square, you'll need to do the same for the suspension.
Pick a point at the outer end of a lower front wishbone, say the head of a bolt (make sure the face of the bolt's vertical).
Repeat for the other three corners, and again, check the diagonals. Also measure the distance from the centreline out to each X. They should mirror
each other, side to side.
This time, there is no room for any discrepancy at all.
If there are differences, the suspension will need adjusting.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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PaulBuz
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| posted on 21/3/03 at 07:12 PM |
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simple enough then.
cheers
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